Showing papers in "Phytopathology in 1992"
TL;DR: Homegrown corn samples were collected from areas with high and low rates of human esophageal cancer in the southern African territory of Transkei for six seasons over the period of 1976-1989, and the most consistent difference in the mycoflora of the corn kernels was the significantly higher incidence of Fusarium moniliforme in corn from high-vs.
Abstract: Homegrown corn samples were collected from areas with high and low rates of human esophageal cancer in the southern African territory of Transkei for six seasons over the period of 1976-1989. The most consistent difference in the mycoflora of the corn kernels was the significantly higher incidence of Fusarium moniliforme in corn from high-vs. low-rate areas. In the 1989 samples, this significant (P<0.01) difference in high- and low-rate cancer areas was 41.2 and 8.9%, respectively, in good (visibly nonmoldy) corn and 61.7 and 21.4%, respectively (...)
723 citations
TL;DR: A polymerase chain reaction (PCR) method has been developed with a 558-bp fragment of the 16S rRNA gene as template DNA and two oligonucleotide primers from conserved regions of this gene for amplification of mycoplasmalike organisms.
Abstract: A polymerase chain reaction (PCR) method has been developed with a 558-bp fragment of the 16S rRNA gene as template DNA and two oligonucleotide primers from conserved regions of this gene The suitability of the system has been tested with 17 isolates of mycoplasmalike organisms (MLOs) maintained in periwinkle (Catharanthus roseus) and with nine MLO samples from field-grown woody plants With DNA preparations enriched in MLO DNA, an amplification product was obtained after 24 cycles from all MLOs maintained in periwinkle No amplified DNA was detected under these conditions in the samples from healthy plants ()
547 citations
TL;DR: Effect of chitosan coating on decay of strawberry fruits held at 13 C was investigated and it was found that decay caused by B. cinerea or R. stolonifer was markedly reduced by chitOSan coating.
Abstract: Effect of chitosan coating on decay of strawberry fruits held at 13 C was investigated Strawberry fruits were inoculated with spore suspensions of Botrytis cinerea or Rhizopus stolonifer and subsequently coated with chitosan solutions (10 or 15 mg/ml) After 14 days of storage, decay caused by B cinerea or R stolonifer was markedly reduced by chitosan coating Decay was not reduced further when the concentration of chitosan coating was increased from 10 to 15 mg/ml Coating intact strawberries with chitosan did not stimulate chitinase, chitosanase, or β-1,3-blucanase activities in the tissue as revealed by polyacrylamide gel assays ()
493 citations
TL;DR: Hydrogen peroxide was generated in vitro by horseradish peroxidase in the presence of NADH or NADPH and guaiacol was also not oxidized in the absence of either H 2 O 2 or peroxIDase.
Abstract: Hydrogen peroxide was generated in vitro by horseradish peroxidase in the presence of NADH or NADPH. When peroxidase was inactivated by heating (30 min at 100 C) or catalase was added to the reaction mixture, little or no hydrogen peroxide was generated as measured by a guaiacol oxidation assay. In the absence of either H 2 O 2 or peroxidase, guaiacol was also not oxidized. Guaiacol oxidation was also observed when either NADH was replaced by NAD and malate in the presence of malate dehydrogenase or NADPH was replaced by NADP and glucose-6-phosphate in the presence of glucose-6-phosphate dehydrogenase (...)
417 citations
TL;DR: Near-isogenic lines (NILs) with single blast resistance genes were developed by backcrossing four donor cultivars to the recurrent parent CO39, and were classified into six groups by their reaction to a diverse set of blast isolates.
Abstract: Resistance to blast disease is an important objective of most rice breeding programs. Genetic studies of resistance have been complicated by variability of the pathogen and lack of rice genotypes with single resistance genes. Near-isogenic lines (NILs) with single blast resistance genes were developed by backcrossing four donor cultivars to the recurrent parent CO39. Five pathogen isolates were used to screen the populations during backcrossing. The 22 NILs were classified into six groups by their reaction to a diverse set of blast isolates (...)
365 citations
TL;DR: F 2 populations or F 3 lines from several intercrosses of wheats carrying Lr34 did not segregate for susceptibility to stripe rust and leaf rust, indicating that at least one resistance gene was common in each parent.
Abstract: Near-isogenic Thatcher lines (viz., RL6058, RL6077, and Line 920) carrying gene Lr34 for leaf rust resistance, Frontana, and various other wheat cultivars carrying Lr34 displayed adult plant resistance to stripe rust in Mexico. F2 populations or F3 lines from several intercrosses of wheats carrying Lr34 did not segregate for susceptibility to stripe rust and leaf rust, indicating that at least one resistance gene was common in each parent. An evaluation of F3 lines for stripe rust and leaf rust, from the crosses of stripe rust and leaf rust susceptible Jupateco 73S with stripe rust and leaf rust resistant Condor and Jupateco 73R, showed linked segregation for the two diseases. For each disease, resistance was conferred by one partially dominant gene. Because Lr34 is located on chromosome 7D, the linked Yr gene is designated Yr18. RL6058, RL6077, Line 920, Condor, or Jupateco 73R could be used as tester genotypes for Yr18. The durable adult plant stripe rust resistance of Anza, a related sib of the parent of Condor, is postulated to be attributable to Yr18, which is widespread in cultivars from the International Maize and Wheat Improvement Center germ plasm and South American wheats. An additional adult plant stripe rust resistance gene was present in both Sonoita 81 and Tonichi 81
272 citations
TL;DR: Two Phytophthora infestans populations in northern Mexico were analyzed for genetic variation by use of mating type, two allozyme loci, and two DNA fingerprinting probes, and were compared to two populations from central Mexico.
Abstract: Two Phytophthora infestans populations in northern Mexico (north-western and northeastern) were analyzed for genetic variation by use of mating type, two allozyme loci, and two DNA fingerprinting probes, and were compared to two populations from central Mexico. The genetic structure of the populations varied widely, even though both mating types occurred in all locations sampled. There was very little genetic diversity in northwestern Mexico; four genotypes were detected among 88 isolates tested, and only two of these were common. All A2 isolates in this population appeared to represent a single clone and were exclusively on potatoes, whereas the A1 isolates were primarily on tomatoes (...)
265 citations
TL;DR: All benomyl-resistant field strains of Venturia inaequalis, V. pirina, Monilinia fructicola, Sclerotinia homoeocarpa, and six species of Penicillium, except those with low resistance to Benomyl, were found to contain a single base pair mutation in their beta-tubulin gene that resulted in an amino acid substitution in beta- Tubulin.
Abstract: All benomyl-resistant field strains of Venturia inaequalis. V. pirina, Monilinia fructicola, Sclerotinia homoeocarpa, and six species of Penicillium, except those with low resistance to benomyl, were found to contain a single base pair mutation in their beta-tubulin gene that resulted in an amino acid substitution in beta-tubulin. In V. inaequalis, codon 198, which encodes glutamic acid in a sensitive strain, was converted to a codon for alanine in a strain with very high resistance, to a codon for lysine in a strain with high resistance, or to a codon for glycine in a strain with medium resistance to benomyl (...)
247 citations
TL;DR: Pseudomonas fluorescens strain CHA0 suppresses various plant diseases caused by soilborne fungi and procedures several antibiotic metabolites, two of which have been identified as pyoluteorin (Plt) and 2,4-diacetyl-phloroglucinol (Phl).
Abstract: Pseudomonas fluorescens strain CHA0 suppresses various plant diseases caused by soilborne fungi and procedures several antibiotic metabolites, two of which have been identified as pyoluteorin (Plt) and 2,4-diacetyl-phloroglucinol (Phl). A cosmid (pME3090) carrying a 22(kb insert of strain CHA0 DNA enhanced, in a CHA0 background, the production of Plt in vitro (...)
233 citations
TL;DR: A cross was made between two field isolates of Magnaporthe grisea pathogenic to rice and genetic analysis of the pathogen revealed that avirulence to the rice cultivar Pi-n o 4 is controlled by one gene (Avr1-Pi- n o 4) unlinked to the gene MATI-1, which is responsible for mating type.
Abstract: A cross was made between two field isolates of Magnaporthe grisea pathogenic to rice. Full-sib crosses between F 1 ascospores, followed by backcrosses to the female fertile parent GUY 11, produced perithecia fertile enough for tetrad isolation. Genetic analysis of the pathogen revealed that avirulence to the rice cultivar Pi-n o 4 is controlled by one gene (Avr1-Pi-n o 4) unlinked to the gene MATI-1, which is responsible for mating type. Additionally, resistance of Pi-n o 4 was found to be controlled by one gene. Thus, existence of a gene-for-gene relationship was shown for the pathosystem Oryza sativa-M. grisea
231 citations
TL;DR: The data are generally consistent with previous work on this mycotoxin, but the differences between the A and F mating populations are significant because both of these groups share the Fusarium moniliforme anamorph.
Abstract: Fungal isolates of Gibberella fujikuroi are economically important as plant pathogens and as producers of mycotoxins. The species can be subdivided into six distinct mating populations that probably represent different biological species. Members of four of these mating populations-A, D, E, and F-are commonly found in asymptomatic and diseased maize and sorghum plants. We tested 56 G. fujikuroi isolates that had been collected in Kansas and assigned to mating populations for their ability to produce the mycotoxin fumonisin B1. When grown on maize grain under laboratory conditions, members of the A population could produce an average of 1,786 ppm of the toxin, members of the population averaged 636 ppm, the E population 33 ppm, and the F population 7.5 ppm. Strain-related variability in fumonisin B, production was relatively large in the A and D populations (307-4,425 and 4-2,618 ppm, respectively) and relatively low in the E and F populations (6-146 and 2-35 ppm, respectively). The level of fumonisin B1 produced by the different isolates did not appear to be related to geographic origin, host, or disease status of the host plant. Our data are generally consistent with previous work on this mycotoxin, but the differences between the A and F mating populations are significant because both of these groups share the Fusarium moniliforme anamorph.
TL;DR: Transmission electron microscopy observations and serological results demonstrate that larval and adult WFT ingest TSWV particles during feeding on infected plants, after which virions can be found within the midgut lumen and epithlial cells.
Abstract: Ultrastructural and serological analyses provide evidence that a midgut barrier underlies the inability of adult western flower thrips (WFT), Frank-liniella occidentalis, to acquire tomato spotted wilt virus (TSWV) through adult feeding on infected plants. As demonstrated for other thrips vector species, only WFT that acquire TSWV as larvae can successfully inoculate plants with the virus as adults. Transmission electron microscopy (TEM) observations and serological results demonstrate that larval and adult WFT ingest TSWV particles during feeding on infected plants, after which virions can be found within the midgut lumen and epithlial cells (...)
TL;DR: Potting mixes prepared with Canadian sphagnum peats varied in suppressiveness to Pythium root rot of poinsettia caused by Pythium ultimum, and microbial activity was highest in the suppressive and lowest in the conducive potting mixes.
Abstract: Potting mixes prepared with Canadian sphagnum peats varied in suppressiveness to Pythium root rot of poinsettia caused by Pythium ultimum. Root rot and population development of P. ultimum were highest in the most decomposed, dark (H 4 on the von Post decomposition scale) peat, intermediate in a slightly decomposed (H 3 ) peat, and suppressed in the least decomposed light (H 2 ) peat. Microbial activity, based on the rate of hydrolysis of fluorescein diacetate (FDA), was highest in the suppressive and lowest in the conducive potting mixes (...)
TL;DR: The extent and nature of the variability of Colletotrichum graminicola can be characterised by random amplified polymorphic DNA marker analysis, a simple and fast technique that permits differentiation among isolates.
Abstract: Colletotrichum graminicola, the causal agent of anthracnose of sorghum, is a highly variable fungal pathogen. The high degree of variability hinders breeding for resistance and optimal deployment of cultivars. The extent and nature of this variability can now be characterised by random amplified polymorphic DNA marker analysis, a simple and fast technique that permits differentiation among isolates
TL;DR: Peroxidase activity in uninfected muskmelon plants was used to predict the resistance and susceptibility of 257 plants, including cultivars or breeding lines and crosses of susceptible and resistant plants.
Abstract: Peroxidase activity in uninfected muskmelon plants was used to predict the resistance and susceptibility of 257 plants, including cultivars or breeding lines and crosses of susceptible and resistant plants. When values of peroxidase activity greater than or equal to 30 (changes in absorbance at 470 nm min -1 g -1 fresh weight of leaf tissue) were used, 100% of the resistant plants were detected, whereas at values of less than 30, 89% of the susceptible plants were detected (...)
TL;DR: Pseudomonas fluorescens Pf-5 protected cucumber from preemergence damping-off caused by Pythium ultimum and produced a number of antifungal metabolites in culture, including a fluorescent siderophore (pyoverdine), pyoluteorin, pyrrolnitrin, cyanide, and an uncharacterized compound termed antibiotic 3.
Abstract: Pseudomonas fluorescens Pf-5 protected cucumber from preemergence damping-off caused by Pythium ultimum and produced a number of antifungal metabolites in culture, including a fluorescent siderophore (pyoverdine), pyoluteorin, pyrrolnitrin, cyanide, and an uncharacterized compound termed antibiotic 3. Of these, the roles of pyoluteorin and pyoverdine in the biocontrol activity of Pf-5 against Pythium damping-off of cucumber were investigated. Tn5 insertion mutants of Pf-5 were screened for loss of pyoluteorin production (Plt - ) or pyoverdine production (Pvd - ) (...)
TL;DR: Morphological characteristics of pseudothecia, asci, and ascospores confirmed the identification as Didymella rabiei rather than Mycosphaerella rabieo, which is heterothallic and has been referred to as MAT1-1 and MAT2-2.
Abstract: The teleomorph of Ascochyta rabiei was induced to develop and mature on artificially infested chickpea straw. High moisture and low temperature (5-10 C) were the major factors required for pseudothecial development and maturation. At 8 C, pseudothecia developed and matured in about 8 wk. Morphological characteristics of pseudothecia, asci, and ascospores confirmed the identification as Didymella rabiei rather than Mycosphaerella rabiei. The fungus is heterothallic, and the two mating types have been referred to as MAT1-1 and MAT1-2 (...)
Journal Article•
TL;DR: It is proposed that endorhizosphere temporary apoplastic (intercellular space) pathway between the is a semantically incorrect term that means different things to cortex and stele at sites of lateral root eruption, thereby providing a studies of root-zone microflora.
Abstract: In recent years, the term endorhizosphere has been used in however, this process takes time (4), thereby providing a studies of root-zone microflora. We propose that endorhizosphere temporary apoplastic (intercellular space) pathway between the is a semantically incorrect term that means different things to cortex and stele at sites of lateral root eruption (6). Peterson different people. et al (21) used fluorescent dyes to trace apoplastic pathways to Hiltner, in 1904, originally used Rhizosphaire to describe the the stele in corn and broad bean roots at various stages of zone of soil under the influence of legume roots (12). Expansion development. Tracer dyes were not found in the stele of healthy, of the rhizosphere concept to other plants soon followed; however, nonwounded primary roots, but they were found in the stele when the term was still used to describe a niche within soil. Herein a secondary root had just emerged from the epidermis of the lies the semantical problem with the term endorhizosphere. With main root. In such cases, dyes moved through the pericycle, moved the base word, rhizosphere, referring to a soil niche, the addition into the root xylem, and were detected in the xylem of stems. of endo would make the word literally refer to an interior zone Peterson et al (21) concluded \"that a continuous apoplastic of the same soil niche. In other words, endorhizosphere describes pathway of transport from the root epidermis to the shoot existed soil, rather than a niche within the host plant. Semantically correct in both corn and broad bean roots.\" The occurrence of even terms to describe the interior of roots would be endoroot, endotemporary continua in the intercellular space between the cortex rhiza, hypoepidermis, or hyporhizoplane. However, as we propose and xylem would be sufficient for movement of microorganisms later, we do not believe that any specialized term is necessary. into the xylem and may account for recent observations of The first use of the term endorhizosphere by Balandreau and saprophytic bacteria in stems after their application to seeds or Knowles in 1978 (1) reflected reports in the early 1970s that the roots. Misaghi and Donndelinger (17) reisolated a rifampicininterior of roots contained bacteria. In their discussion, resistant mutant of one Erwinia sp. strain from cotton stems, Balandreau and Knowles cited work of Old and Nicholson (19,20), flowers, and bolls stems after inoculation by vacuum infiltration which in turn cited reports by Darbyshire and Greaves (5,11). of emerged radicles. In 1973, Darbyshire and Greaves (5) stated, \"as microbes inside Second, even as there is a continuum of root-associated plant roots can probably affect the metabolism and particularly microorganisms from the rhizosphere to rhizoplane to epidermis the exudation of the host plant, it would seem reasonable in and cortex, so is there a continuum from the endodermis to the the future to consider them as part of the rhizosphere community.\" root xylem and to the stem. Campbell and Greaves (3) reflected Old and Nicholson (19) reported internal populations of bacteria a commonly held view when they stated, \"microorganisms in the in a study using electron microscopy, and, based on their finding stele are almost invariably pathogens.\" However, saprophytic of bacteria in root cortical tissues and in pits of the endodermis, bacteria are also found in the stele and can move to different they supported modification of the rhizosphere concept to include plant organs. Bacteria have been isolated from the interior of soil microorganisms that penetrate plant roots. healthy plants, including ovules (18), seed pieces, and stems of The first published usage of the term endorhizosphere occurred potato (13); taproot of clover (22); roots of sugarbeet (14); and as a section heading in a review on the rhizosphere (1); however, roots of alfalfa (7,8). With alfalfa, Pseudomonas spp., Erwiniano definition of endorhizosphere was proposed in this section, like spp., gram-positive strains, and other unidentified gramwhich discussed general bacterial and fungal invasion of root negative bacteria were consistently isolated from root xylem (7) tissues. The first review that cited endorhizosphere was by Lynch at populations of logl0 3-4 cfu/g. The effects of 33 of these vascular (15), who stated, \"the root-epidermis-cortex zone, when colonized endophytes on plant growth were investigated in a separate study by pathogens or non-pathogens, has been termed the 'endorhizo(8). One strain induced a significant reduction in root development sphere' by Balandreau and Knowles.\" As previously indicated, and yield, whereas another significantly increased both paramBalandreau and Knowles did not define the term. Therefore, it eters. Hence, bacteria within the root stele, and therefore not is unclear who should be cited as the original source of the term included in the current definition of endorhizosphere, may have endorhizosphere and what the original definition is. In any case, the same positive effects on plants as rhizosphere bacteria. the original idea of Darbyshire and Greaves (5) to consider The most extensive work with population dynamics of xylemmicroorganisms inside roots as part of the rhizosphere community inhabiting bacteria is found in the reports from Gardner and was somehow transformed to consider only the microorganisms colleagues in 1982 (10) and 1985 (9) with citrus trees. Thirteen specifically in the root epidermis and cortex. genera were represented among 556 strains, the most frequent In addition to the semantical problem and historical confusion, being Pseudomonas (40%); Enterobacter (18%); and Bacillus, we believe that the term endorhizosphere should not be used Corynebacterium, and other gram-positive bacteria (40%). Inocufor the following four reasons. lation of pruned roots with 19 randomly selected strains resulted First, the proposed limitation of the endorhizosphere to the in significant growth inhibition of shoots by seven strains. Two cell layers between the epidermis and endodermis is apparently strains induced a significant increase in shoot growth. These results based on the premise that the endodermis forms an impenetrable further demonstrate that xylem-inhabiting bacteria may also be barrier to bacteria. Several lines of evidence suggest that this beneficial to the plant and, therefore, are not always pathogens. is not the case. In the process of lateral root growth from the In the past few years, several reports have been published on pericycle to the epidermis of the primary root, the endodermis bacterial endophytes. Sunyun and Yanxi at Beijing Agricultural and its Casparian strips are disrupted (4). Redifferentiation of University (24) reported that Bacillus spp., Xanthomonas spp., endodermal cells occurs between the parent and lateral roots; and Erwinia spp. were common endophytes of cotton infested with the Fusarium wilt pathogen. At another university in China, © 1992 The American Phytopathological Society Xiao et al (27) reported that endophytic bacteria could be isolated
TL;DR: Two metabolites with antifungal activity against Pythium ultimum, 2-(buta-1,3-dienyl)-3-hydroxy-4-(penta-3- dienyl-tetrahydrofuran) and the epidithiadiketopiperazine, chaetomin, were isolated from liquid cultures of C. globosum.
Abstract: Production of antifungal compounds by Chaetomium globosum and the role in suppression of Pythium damping-off of sugarbeet were evaluated. Two metabolites with antifungal activity against Pythium ultimum, 2-(buta-1,3-dienyl)-3-hydroxy-4-(penta-1,3-dienyl)-tetrahydrofuran (BHT) and the epidithiadiketopiperazine, chaetomin, were isolated from liquid cultures of C. globosum. BHT was produced in 1% malt extract medium by six of eight tested C. globosum strains, whereas chaetomin was produced in 1% corn steep medium by five of nine tested strains (...)
TL;DR: Clonal variability within and among field populations of Sclerotinia sclerotiorum isolated from canola petals in western Canada was determined by analysis of two independent criteria, mycelial compatibility and DNA fingerprinting.
Abstract: Clonal variability within and among field populations of Sclerotinia sclerotiorum isolated from canola petals in western Canada was determined by analysis of two independent criteria, mycelial compatibility and DNA fingerprinting. Strains were considered to belong to the same clone if they were mycelially compatible and also had identical DNA fingerprints. Thirty-nine clones were identified among 66 strains from seven locations in Alberta, Saskatchewan, and Manitoba. The most widely distributed clone, accounting for 18% of the isolates, was found in all three provinces (...)
TL;DR: Four hundred sixty-seven Magnaporthe grisea isolates were collected from rice in 34 countries, and most of these isolates do not produce perithecia with any of the four fertile testers.
Abstract: Four hundred sixty-seven Magnaporthe grisea isolates were collected from rice in 34 countries. Each isolate was tested for mating type with two MAT1-1 and two MAT1-2 fertile (hermaphroditic) standard isolates. Thirty-two percent of these isolates are MAT1-1, and 20% are MAT1-2. The remaining 48% do not produce perithecia with any of the four fertile testers. In most locations, only one mating type was present. In two locations (one in Ivory Coast and one in Cameroon), isolates of both mating types were found, but they were intersterile
TL;DR: The physiological differences of the newly found whitefly biotype, including host preference, larval development, transmission of lettuce infectious yellows virus, and the induction of silverleaf symptoms, clearly distinguish it from the previously occurring biotype.
Abstract: Collections of Bemisia tabaci from California desert regions have been shown to be a mixture of biotypes. These whitefly biotypes differ in a number of ways including their ability to induce silverleaf of squash. The physiological differences of the newly found whitefly biotype, including host preference, larval development, transmission of lettuce infectious yellows virus, and the induction of silverleaf symptoms, clearly distinguish it from the previously occurring biotype (...)
TL;DR: Three strains of Colletotrichum gloeosporioides from citrus in Florida are described and characterized as fast-growing gray isolates from necrotic and senescent tissue, slow-growing orange isolates associated with citrus postbloom fruit drop disease, and slow- growing isolates with deep orange pigmentation from Key limes affected by lime anthracnose.
Abstract: Three strains of Colletotrichum gloeosporioides from citrus in Florida are described and characterized as fast-growing gray isolates from necrotic and senescent tissue (FGG), slow-growing orange isolates (SGO) associated with citrus postbloom fruit drop disease, and slow-growing isolates with deep orange pigmentation from Key limes affected by lime anthracnose (FLA) (formerly classified as Gloeosporium limetticola). All FGG isolates had large conidia most with both apices rounded, produced abundant setae, and had large lobulate appressoria (...)
TL;DR: Mixtures of two, three, four, or five winter wheat cultivars and their component pure stands were either exposed to or protected from two stripe rust races at three and two locations in 1986-1987 and 1987-1988.
Abstract: Mixtures of two, three, four, or five winter wheat (Triticum aestivum) cultivars and their component pure stands were either exposed to or protected from two stripe rust (Puccinia striiformis) races at three and two locations in 1986-1987 and 1987-1988, respectively. Disease severity and yield components per cultivar were determined for a subset of the mixtures and also for the pure stands. Disease severity in the mixtures compared to the mean of the components was reduced between 13 and 97%. Changes in disease severity could be separated into two effects. First, selection changed frequencies of the cultivars in the mixtures by up to 35% at harvest compared to the planted frequencies (...)
TL;DR: Pseudomonas fluorescens 2-79 (NRRL B-15132) and its rifampicin-resistant derivative 2- 79RN 10 are suppressive to take-all of wheat caused by Gaeumannomyces graminis var.
Abstract: Pseudomonas fluorescens 2-79 (NRRL B-15132) and its rifampicin-resistant derivative 2-79RN 10 are suppressive to take-all of wheat caused by Gaeumannomyces graminis var. tritici. Production of the antibiotic phenazine-1-carboxylic acid (PCA) is the primary mechanism of suppression by this strain, while a fluorescent siderophore and a second iron-regulated factor have minor roles. Hyphal growth of G. g. tritici was inhibited by strain 2-79RN 10 on modified Kanner agar (KMPE) (used for PCA production) adjusted to several pH values within the range of 4.9 to 8.0 (...)
TL;DR: The effects of 10 different foliar diseases on the photosynthetic and transpirational activities of five annual and three perennial crops were examined under field conditions.
Abstract: The effects of 10 different foliar diseases on the photosynthetic and transpirational activities of five annual and three perennial crops were examined under field conditions. The following pathosystems were investigated: leaf rust, powdery mildew, and Septoria tritici blotch of wheat; rust of corn; downy mildew of cucumber; Alternaria leaf spot of cotton; powdery mildew of pepper; Pestalotia of mango; powdery mildew of peach; and powdery mildew of grapes. Visual estimates of infection do not always indicate adequately the effect of a pathogen on these physiological processes (...)
TL;DR: Inheritance of stripe rust resistance in 13 wheat cultivars used to differentiate races of Puccinia striiformis in North America was determined using nine North American races of the pathogen.
Abstract: Inheritance of stripe rust resistance in 13 wheat (Triticum aestivum) cultivars used to differentiate races of Puccinia striiformis in North America was determined using nine North American races of the pathogen. The differential cultivars, which were resistant to specific races, were crossed with cultivars susceptible to the specific races. We found that Lemhi, Chinese 166, Riebesel 47/51, and Tyee each have a single resistance gene; Heines VII, Moro, Druchamp, Produra, Stephens, Lee, and Fielder each have two resistance genes; and Paha and Yamhill each have three resistance genes (...)
TL;DR: Thirty-six carbohydrates and twenty-three nitrogenous compounds were evaluated for their effect on germination, and germ tube and radial growth of the pathogen Penicillium expansum, and for stimulation of growth of an antagonist Pseudomonas syringae.
Abstract: Thirty-six carbohydrates and twenty-three nitrogenous compounds were evaluated for their effect on germination, and germ tube and radial growth of the pathogen Penicillium expansum, and for stimulation of growth of an antagonist Pseudomonas syringae (strain L-59-66). Compounds that strongly stimulated growth of the antagonist but had little or no stimulatory effect on germination and growth of the pathogen were evaluated for their effect on enhancing biocontrol of blue mold on ripe Golden Delicious apple. Seven amino acids and two carbohydrates met the required criteria (...)
TL;DR: Soybean plants dually infected with SMV and either one of two comoviruses, cowpea mosaic virus (CMPV) or bean pod mottle virus (BPMV), showed greatly increased symptom severity over that induced by the individual viruses.
Abstract: Soybean plants dually infected with soybean mosaic potyvirus (SMV) and either one of two comoviruses, cowpea mosaic virus (CMPV) or bean pod mottle virus (BPMV), showed greatly increased symptom severity over that induced by the individual viruses. The titer of the comovirus (but not of SMV) in the dually infected plants was significantly higher than that in singly infected plants. Electron microscopic examination of thin sections of leaves from dually infected plants revealed that both SMV and CPMV (or BPMV) were present in the same cells (...)
Journal Article•
TL;DR: Chitosan was found to inhibit the radial growth of F. o.
Abstract: The effect of chitosan on the growth, morphology, and ultrastructure of Fusarium oxysporum f. sp. radicis-lycopersici was investigated. Chitosan was found to inhibit the radial growth of F. o. radicis-lycopersici with an optimal effect at concentrations ranging from 3 to 6 mg/ml. Light microscope observations showed that chitosan induced morpholocical changes, including hyphal swelling and distortion. Ultrastructural changes observed in chitosan-treated cells included alteration of the plasma membrane and pronounced aggregation of the cytoplasm (...)